The subject matter described herein generally relates to neurostimulation (NS) systems and NS devices for generating electric fields proximate to nervous tissue.
NS systems are configured to generate electrical pulses and deliver the pulses to nervous tissue to treat a variety of disorders. Spinal cord stimulation (SCS) is a common type of neurostimulation. In SCS, electrical pulses are delivered to nervous tissue in the spine to generate electric fields that can treat a neurologic condition. For example, the application of an electric field to spinal nervous tissue can effectively mask or alleviate certain types of pain transmitted from regions of the body associated with the stimulated nervous tissue.
Conventional NS systems may include a pulse generator and one or more elongated leads that are electrically coupled to the pulse generator. Each elongated lead includes a stimulating end, a trailing end, and an intermediate portion that couples the stimulating and trailing ends. The elongated lead may be cable-like and extend, for example, up to sixty centimeters or more between the stimulating and trailing ends. The stimulating end may have a body with multiple electrodes that are configured to interface with nervous tissue, such as within an epidural space of a spinal cord. The trailing end includes multiple terminal contacts that engage corresponding contacts of the pulse generator. The terminal contacts of the trailing end and the electrodes of the stimulating end are coupled by wire conductors that extend through the intermediate portion. In use, the pulse generator controls current through the wire conductors to generate the electric fields along the nervous tissue. The pulse generator is typically implanted within the patient in a subcutaneous pocket formed near the surface of the skin. The pulse generator may be programmed (and re-programmed) to provide the electrical pulses in accordance with a designated sequence.
Typically, one of two types of leads is used. The first type is a percutaneous lead, which has a rod-like shape and includes electrodes spaced apart from each other along a single axis. The second type of lead is a laminectomy or laminotomy lead (hereinafter referred to as a paddle lead). A paddle lead may have an elongated and generally planar body with a substantially rectangular shape (i.e., paddle-like shape). Paddle leads typically include an array of electrodes that are spaced apart from each other. The number of electrodes may be, for example, four, eight, sixteen, or more.
Although such NS systems can be effective for treating one or more neurologic conditions, some drawbacks or challenges may exist. For example, NS systems may be prone to heating and induced currents when placed within strong gradient and/or radiofrequency (RF) magnetic fields of a magnetic resonance imaging (MRI) system. The heat and induced currents result from the metal components of the leads functioning as antennas in the magnetic fields. Components of the system may also move due to the force/torque generated in the static magnetic field of an MRI system.
In addition to the above, the number of components and overall shape and size of a conventional NS system may increase the likelihood of infection or require a follow-up surgery for the patient. For instance, in order to implant the entire NS system, the elongated lead is tunneled from the epidural space through the body and into the subcutaneous pocket where the pulse generator is located. NS systems that do not require tunneling and a subcutaneous pocket may reduce the likelihood of infection and/or a follow-up procedure being necessary.